1. Field of the Invention
The present invention relates to a color filter array for an image sensing device and manufacturing method thereof, and more particularly, to a color filter array capable of enlarging a dynamic range of an image sensing device and the manufacturing method thereof.
2. Description of the Prior Art
Image sensing devices are widely utilized in digital electronic products, such as scanners, digital cameras, mobile phones and personal digital assistants. The most common types of image sensing device are Complementary Metal Oxide Semiconductors (CMOS) and Charge Coupled Device (CCD). These image sensing devices are both silicon semiconductor devices utilized for sensing light and transferring the sensed light into electricity. The electricity generated by the image sensing device is transferred into measureable voltages, from which digital data can be acquired.
Please refer to FIG. 1, which is a characteristic diagram of the luminous flux received by a conventional image sensing device and the voltage generated by the conventional image sensing device. The voltage corresponds to the image information sensed by the image sensing device. As shown in FIG. 1, the image sensing device transfers the luminous flux to a measureable voltage once the luminous flux received by the image sensing device exceeds a minimum luminous flux LFmin. In other words, the image sensing device acquires valid image information when the luminous flux received by the image sensing device during an image sensing time period exceeds the minimum luminous flux LFmin. Thus, if the minimum luminous flux is made smaller, the image sensing device may acquire image information corresponding to less luminance.
The image sensing generates a maximum voltage Vmax when the luminous flux received by the image sensing device exceeds a maximum luminous flux LFmax. In other words, the image sensing device outputs maximum voltage Vmax when different image information having corresponding luminous flux exceeding the maximum luminous flux LFmax are received by the image sensing device. In such a condition, the different image information cannot be identified. Therefore, when the maximum luminous flux LFmax becomes higher, the luminous flux range of the image information which can be identified by the image sensing device becomes broader. The prior art provides a dynamic range (DR) as an indicator for evaluating the luminous flux range of the image information which is capable of being identified by the image sensing device, i.e. the range of the luminous flux which is received by the image sensing device and is capable of being identified by the image sensing device. The dynamic range is defined as:
      D    ⁢                  ⁢    R    =      20    ⁢                  ⁢          Log      ⁡              (                              L            ⁢                                                  ⁢            F            ⁢                                                  ⁢            max                                L            ⁢                                                  ⁢            F            ⁢                                                  ⁢            min                          )            
Generally, when the dynamic range of the image sensing device increases, the luminance differences in the image information which can be sensed by the image sensing device become greater. Thus, how to increase the dynamic range of the image sensing device becomes a topic to be discussed.